Rhodopsin will be subject to digestion by a number of proteolytic enzymes including papain, pronase, and thermolysin. Peptides will be isolated chromatographically and the spectral properties, particularly the CD spectra, of the fragments will be measured. Analogs of retinal will be used to study the binding of retinal to the peptide fragments in order to obtain values for the energy of interaction of chromophore and protein. The fragments will be irradiated at low temperatures and bleaching intermediates, analogous to batho-, lumi-, and meta pigments, will be sought. The peptide fragments will be incorporated into lipid vesicles and the ion permeabilities will be characterized. Crustacyanin will be isolated from lobster shells and the aproprotein prepared. Isomers of retinal and analogues of retinal will be added to the protein and the UV-visible and CD spectral properties of the resulting retinal--crustocyanin (RCC) pigments will be measured. RCC pigments will be purified and crystallized. Tryptophan residues in opsin will be oxidized by N-bromo succinimide (NBS). 11-cis retinal will be added to the altered protein and the rate of regeneration will be measured as well as the CD spectrum of any resulting pigment. The thermodynamics of retinal bonding will be studied with 11-cis retinal, which is expected to behave as a competitive inhibitor of 11-cis retinal binding. Retinal analogues will also be tested.